Dual-drop printing is achieved using two or more full length waveforms and a predetermined jet geometry that generates two or more different drop masses from each jet for a given page.
Dual-drop mode refers to the ability of the printhead to generate two or more different drop masses. However, only one of these masses is typically used in a given image. This is accomplished with the use of separate full length waveforms that achieve different drop masses for any given jet nozzle. For example, the Phaser 340, available from Xerox Corporation, used this to achieve a 110 ng drop and a 67 ng drop by firing one of the two waveforms depending on a mode of operation. In order to achieve the smaller drop with the same jet geometry, the smaller drop waveform was run at a lower frequency.
Drop-size-switching (DSS) refers to the ability of a jet to generate a multitude of drop masses (two, for example) on-the-fly. This can be accomplished by fitting two half (½) length waveforms into the jetting time 1/fop. Here “fop” refers to “frequency of operation”, which is the frequency at which drops eject from each jet of a print head when firing continuously. The electronics select one of the two waveforms according to one or more patterning methodologies to print a page length document. This achieves printing from individual jet nozzles of either a large drop or a small drop.
As shown in FIG. 1, a printhead driver 200 incorporates two separate waveforms (waveform 1 and waveform 2) into a single print firing period (1/fop). One of the two waveforms is selected “on the fly” by driver 200 to drive individual jets of printhead 100 based on specific image criteria or image quality. Printhead 100 includes an aperture plate 110 and a diaphragm plate 120. A piezoelectric transducer 130 is provided on the diaphragm plate 120. Between the two plates 110, 120 are defined ports 140, feed lines 150, manifold 160, inlet 170, body 180, outlet 185, and apertures 190. An example of this type of “on the fly” printhead is further described in U.S. Pat. No. 5,495,270 to Burr et al., the disclosure of which is hereby incorporated herein in its entirety.
This concept was introduced in the Phaser 850 Enhanced Mode, also available from Xerox Corporation. Both a 51 ng and a 24 ng drop size could be generated “on the fly.” However, in this design, the printhead ran at the slower frequency of the small drop. Because the smaller drop ran at a lower frequency, it could not be printed at high speed. However, because the large drop was available to allow an overall reduction in resolution while maintaining appropriate total solid coverage, the dual-drop mode worked and was beneficial.